1. Field of the Invention
The present invention relates to a receiver in a wireless communication system and, more particularly, to a receiving apparatus and method for removing channel interference in a wireless communication system.
2. Description of Related Art
A receiver of a wireless communication system requires 3 types of conversions including the frequency down-conversion to convert an RF signal (radio frequency signal) to a baseband signal, the sampling conversion (ADC) to convert an analog signal baseband signal to a digital signal, and the quantization conversion.
FIG. 1 is a schematic block diagram of a conventional receiver in a wireless communication system. Referring to FIG. 1, the receiver 10 comprises an antenna 15, a RF tuner 20, an analog-digital conversion (ADC) block 30, a channelization filter 40, an equalizer 50 and a channel estimator 60. The RF tuner 20 tunes to a frequency of a channel that is intended to be received through the antenna 15 and converts the tuned frequency RF signal into a baseband signal (having a baseband frequency range). The analog-digital conversion (ADC) block 30 converts an analog baseband signal Sa (having the baseband frequency range) into a digital baseband signal.
The channelization filter 40 selects and outputs only the signal of a desired band among the digital (baseband) signals and having a predetermined bandwidth at a predetermined center-frequency and a predetermined sample rate. The equalizer 50 receives the signal output from the channelization filter 40 and regenerates the high frequency component of the received signals which is attenuated by dispersion of pulse caused by reduction or distortion due to transmission media, based on the channel information from the channel estimator 60. The channel estimator 60 receives the signal output from the channelization filter 40 and estimates channel information such as the channel transfer function and provides it to the equalizer 50.
The performance of the wireless communication system (for example, Global System for Mobile Communication and Enhanced Data Rates for GSM Evolution) is deteriorated by various interferences that may occur in the wireless communication environment, and thus a technical countermeasure against such interferences is needed.
Generally, the interference that may occur in the wireless communication system includes co-channel interference and adjacent-channel interference. The co-channel interference includes interference between base stations using a same frequency and interference from other systems such as undercover stations. The adjacent-channel interference includes interference between base stations in a same system using adjacent frequencies and interference between adjacent systems.
Some areas such as an urban downtown, where numerous users are present, need a higher number of base stations in a relatively small area and may have the co-channel interference by a frequency reuse cell and the adjacent channel interference by a user of an adjacent channel.
Since the interference occurs in the unit of burst in the wireless communication using time division multiple access (TDMA), there is no correlation with interference between bursts. Therefore, it is desired to have a method for independently removing interference within each unit of burst.
In the wireless communication system, a receiver should be provided with an interference removing means for removing the above-described co-channel interference or adjacent-channel interference. A channel condition is classified into a channel having thermal noise (hereinafter referred to as “static channel”) or a channel having ghost or multi-path fading (hereinafter referred to as “fading channel”).
If a filter is selected to remove the channel interference by applying predetermined reference values without regard to the condition of the channel, there would be differences in sensitivity and performance of the receiver according to whether the channel is affected by adjacent-channel interference or co-channel interference.
Particularly, a receiver has less sensitivity for the static channel than for the multi-path channel.